This invention relates to a device for use on vehicles equipped with hydraulic brakes, and is adapted to vary the braking force on vehicle wheels depending upon the wheel load as well as the shifting of the weight of the vehicle.
More particularly the present invention relates to a device of the type adapted to be interposed between rear wheel brakes and one of dual master cylinders for separate hydraulic circuits to front and the rear brakes, for not only sensing the axle loading and the weight shift in order to optimize braking effectiveness but also permitting unrestrained passage of fluid therethrough in order to compensate an accidental failure of the front brakes.
Devices are known for providing a ratio, such as 7 to 3, of braking forces on front and rear wheels when the pressure from the master cylinder reaches a predetermined threshold value in case of deceleration of the vehicle by means of the brakes.
Also it has been known in the art to modulate the threshold value in accordance with variation of the axle loading in order that a closer approximation of a desired relationship between front and rear braking may be provided than possible depending only upon the weight shift. In order to attain such modulation, it has been the practice in the art to employ a spring means attached to a vehicle chassis for sensing the axle loading by the height of the chassis therefrom in partially proportioning the braking pressure coactingly with the proportioning depending upon the weight shift.
The devices currently in use are in any case not entirely satisfactory in that any of them tends to subject the load sensing spring to an uncompromizing increase of load when in case of an accidental failure of the front brakes, so that possibility of ruin exists for the load sensing spring means.